Using the internet for rapid investigation of an outbreak of diarrhoeal illness in mountain bikers.

In summer 2008, we investigated an outbreak of diarrhoeal illness in participants of a mountain-bike event in Wales (UK) which had been affected by heavy rain. We conducted a retrospective cohort study to investigate the cause using an internet-based questionnaire. Fifty-three percent of those contacted responded, and 161 (46·5%) out of the 347 responders, reported gastrointestinal symptoms. Median day of onset was 3 days following the event. Ten riders reported receiving a laboratory-confirmed diagnosis of Campylobacter. Multivariate logistic regression analysis identified the inadvertent ingestion of mud (OR 2·5, 95% CI 1·5-4·2, P<0·001) and eating 'other' food during the event (OR 2·1, 95% CI 1·2-3·6, P=0·01) as significant risk factors for illness. We concluded that the outbreak was caused by Campylobacter, spread to the riders by the inadvertent ingestion of mud which had been contaminated with sheep faeces from the rural course. Mountain-bike race organizers should consider microbiological hazards when risk-assessing potential race courses. The internet is an efficient tool for the investigation of outbreaks in computer-literate populations.